Cocatalysis by ruthenium(III) in hydrogen ions catalyzed oxidation of iodide ions: A kinetic study

Abstract

RuCl 3 further catalyzes the oxidation of iodide ion by K 3 Fe(CN) 6 , already catalyzed by hydrogen ions. The rate of reaction, when catalyzed only by hydrogen ions, was separated graphically from the rate when both Ru(III) and H + ions catalyzed the reaction. Reactions studied separately in the presence as well as absence of RuCl 3 under similar conditions were found to follow second-order kinetics with respect to [I − ], while the rate showed direct proportionality with respect to [Fe(CN) 6 ] 4− ions retards the reaction velocity, while changing the ionic strength of the medium has no effect on the rate. With the help of the intercept of the catalyst graph, the extent of the reaction that takes place without adding Ru(III) was calculated and it was in accordance with the values obtained from the reaction in which only H + ions catalyzed the reaction. It is proposed that ruthenium forms a complex, which slowly disproportionates into the rate-determining step. Arrhenius parameters at four different temperatures were also calculated. C

Iridium(III) catalyzed oxidation of iodide ions in aqueous acidic medium

“…Oxidation of iodide ion by (loxo) diiron (III, III) complexes in weakly acidic medium [27] and by various iron(III) complexes in acetonitrile has been reported and it has been shown that trace levels of copper ions are the potent catalysts for the reaction [28,29]. Oxidation of iodide ions by hexacyanoferrate(III) has already been reported by us in which first order kinetics with respect to [K 3 Fe(CN) 6 ] and [H + ] ions and second order with respect to [I ) ] was observed, when the reaction is catalyzed by palladium(II) in hydrochloric acid [30] and ruthenium(III) in sulphuric acid medium [31]. The present study was performed with the aim of studying the catalytic efficiency of iridium(III) chloride and to see whether the source of hydrogen ions also affects the nature of this reaction or not.…”

“…Production of I 2 ) AE ion in aqueous [19,25,26] and in acetonitrile medium [28,29] has already been reported. Alternatively [30,31] hydrogen ion in the pre-equilibrium step with iodide ion may give rise to HI 2 ) , which may react with Fe III giving rise to reduced Fe II and HI 2 AE . This ion may break up in the slow step to give I 2 ) AE and a proton.…”

Hexacyanoferrate(III) oxidation of arsenic and its subsequent removal from the spent reaction mixture

“…It is known that IrCl 3 in HCl medium gives IrCl 6 3− species [15,16] 3 ] species [17] as shown by the following equilibrium.…”

“…Hexacyanoferrate(III) has long been used as an oxidant presumably due its cheap availability, less complexity involved in the estimation and its capability to act in acidic and alkaline medium both [4]. Based on the assumption that slight interaction of the electronic levels of oxidant and reductant is sufficient to permit electron transfer hexacyanoferrate(III) functions in the oxidation-reduction reactions as a simple one electron abstracting reagent and oxidation invariably occurs via a direct Recently from our laboratory oxidation of iodide ion by hexacyanoferrate(III) has been reported in the presence of Pd(II), Ru(III), and Ir(III) in the presence of various acids like hydrochloric acid, sulphuric acid and perchloric acid [5][6][7].…”

Mechanistic study of the oxidation of l-phenylalanine by hexacyanoferrate(III) catalyzed by iridium(III) in aqueous alkaline medium

“…In recent years, interest in the oxidation of inorganic [1] and organic substrates [2] by hexacyanoferrate(III) (HCF) has been growing. These studies revealed that oxidation by the HCF ion generally proceeds through an outer sphere electron transfer mechanism, which depends not only on the nature of the substrate but also on the medium of the reaction.…”